In the lapping and polishing of read/write heads for the hard disk drive (HDD) industry, very hard and very soft, complex materials are typically finished simultaneously. The very soft materials make up the read/write transducer and are located at the edge of the very hard alumina titania carbide (AlTiC) material. Because high pressures are required to remove the hard AlTiC material, high pressures of up to 40 pounds per square inch (psi) are applied. Such a load on the work-piece causes a displacement of the abrasive surface if the abrasive matrix is of sufficiently low modulus. Compression of the abrasive matrix causes displacement and a wave of abrasive material at the edges of the work-piece. The high stresses at the edge of the work piece causes accelerated removal of the edges or what is commonly called “crown” or edge roll off. This crowning effect can damage the transducer that lies at the edge of the work-piece. Multilayer abrasive articles having compliant pressure sensitive adhesives can exacerbate the crown of a read/write head.
FIG. 1 shows a typical prior art system of an abrasive article 10 having abrasive particles 12 dispersed in a binder 13 on a first surface 18a of a flexible backing 18 having an adhesive layer 14 coated on a second surface 18b of the abrasive article. The adhesive layer, such as, e.g., a pressure sensitive adhesive layer, secures the abrasive article to a rigid support 22. When comparing the various components in the abrasive article 10, the adhesive layer is softer (i.e., having a lower Young's modulus) as compared to the flexible backing and the abrasive particles.
As shown in FIG. 2, in use, typically a work-piece 20 is exposed to the abrasive particles 12 under a load P. Under such circumstances, the work piece and the load applied thereon deform the relatively soft adhesive layer. The flexible substrate tends to follow the deformation of the adhesive layer to cause high stresses at the edges of the work-piece, thereby causing higher material removal rate at the edges of the work-piece. The higher removal rate in turn causes crowning of the work-piece, which is highly undesirable. The edges of the work-piece are rounded due to the high stress caused by the deformation of the underlying adhesive layer and or the deformation of the flexible backing and abrasive particles.